Rjszdorfer



Dec. 17, 1935. o. RISZDORFER 4,

APPARATUS FOR CONTROLLING PHOTOGRAPHIC EXPOSURES I Original Filed Oct.2611930 2 Sheets:Sheei l l935- o. RISZDORFER ,6

APPARATUS FOR CCNTROLLING PHQTOGRAPHIC EXPOSURES Original Filed Oct. 23,1930 2 Sheets-Sheet 2 Patented Dec. 17, 1935 UNITED STATES PATENT OFFICEAPPARATUS ron comoumo PHOTOGRAPHIC EXPOSURES Odon Riszdorfer, Budapest,Hungary Claims.

This invention relates to an arrangement for the automatic regulation ofthe length of time of exposure in taking photographic pictures, forwhich purpose a photo cell is employed.

This application is a division *of my application Serial Number 490,766filed October 23, 1930 which issued September 25, 1934 as Patent No.1,974,433.

In photographing scenes under different lighting conditions it isdifilcult to estimate correctly the exposure which should be used toinsure the best possible results. The subject matter of many scenes aswell as thelimitations of the camera objective employed makes itdesirable in many instances to adjust the diaphragm of the objective forthese factors and to control the exposure by varying the exposureperiod.

It is an object of my invention to provide for photographic apparatus adevice including a light sensitive cell which will govern the exposureperiod to insure proper exposure when a known diaphragm opening is usedand the sensitiveness of the film is also known. Other features andadvantages of my invention will appear from the following descriptionwhen read in connection with the accompanying drawings, and its scopewill be pointed out in the appended claims. r

In the accompanying drawings like characters of reference indicate likeparts in the several views and Figure -l is a perspective view, partlybroken away, showing a camera equipped with one form of the invention.

a Figure 2 is a detail view, partly in section, of certain elements usedin the form shown in Figure l.

Figure 3 is a diagrammatic view of one arrangement of the device asshown in Figure 1.

Figure 4 is a diagrammatic view showing a somewhat different arrangementof the parts of Figure l.

In the arrangement shown in Figure 1, which is well adapted for timeexposures, 43 is the casing wherein is supported the mounting for theshutter 44, object lens 83 and the diaphragm, these parts being of usualconstruction. A photo-ce1l'45 is arranged in the telescopic tube 46 andis exposed through the lens 41. Arranged behind this lens 41 is an irisdiaphragm 41' as shown in Figure 4. This diaphragm is opened and closedby means of a1 toothed wheel 48 and is completely shut before and afterexposure.- One of the terminals 49 ofthe photocell is connected with thesource of current 5| 'in full lines and raised in dotted lines.

by means of a wire 50. The other terminal 52. is connected in serieswith the armature 53, the regulatable resistance 54 and with the otherpole of the source of current 5| through the electromagnet 55 (Figures 2and 4). A clock 5 workmechanism 56 arranged in the casing 43' operatesthe diaphragm 48 of the photo-cell 45 by means of toothed wheels5'I.-and 58. The control for the mechanism is shown in Figure 2. Tostart the mechanism, the button 59 is pushed down. The button 59 carriesa bolt 80. Figure 2 shows the button 59 in pressed-down position Thebolt 60 of the button, after the resistance of the spring 5| has beenovercome, moves into its pressed down position, in which it pressesagainst pins 62 and 63, whose function will be hereinafter more fullyexplained. 64 is a locking pin which, through the pressure of the spring55, is urged into locking position, but which is retracted out of suchlocking position, when the current becomes sufllciently strong by meansof an electro-magnet 55 which acts upon the bolt' head 66 functioning asan armature. The bolt 60 in its pressed-down position, closes thecircuit 59 by means of contacts 51 and 68 and. breaks the circuit bymoving upwardly when locking bolt 65 is being retracted.

Connected to the telescopic tube'45 of the photo-cell is a secondtelescopic tube 69. 111530 other words, the slidable tube members 84 and85 of the said telescopic tubes are attached to each other. The twotubes are "arranged parallel to each other. Telescopic tube 59 has atits front end a lens 10. In its back portion the telescopic tube 84 isprovided with a small mirror II and is connected to a slide 12 which isslidingly arranged, on the outer wall of the camera. Disposed in a holeof the slide above the mirror is a search-lens 13. The slide I2 can beshifted in the direction of the axis of the tube 69 with the result thatthe mirrort'll can be moved closer to or further away from the lens Ill.The tube 85 of the photo-cell automatically participates in thisshifting motion. The shifting is done by means of a pinion 14 whichengages a rack 15. The control device mounted on the casing 43 adjacentthe slide I2 is, by means of the flexible shaft I5, connected with thereleasing mechanism of the shutter of the object lens. This releasemechanism is of the usual type wherein the pressure of a button releasesthe shutter.

The tension of the spring of the mechanism is regulated through turningof the knob 8|. 55

. The pointer of the knob ti movesover a scale will be tensioned. Tofacilitate the operation it is advisable to graduate the scale 82 inconformity with the opening diameters of the diaphragm to be selected.

The apparatus described above is constructed for time exposures, i. e.particularly for use in studios, and operates as follows:

After the diaphragm of the object lens 83 has been set and the springtensioned through turning the knob 8|, the button 59 is pushed down,whereupon the stop 17 of-the bolt 60 forces the pin 62 against thespring 18 in the direction of the arrow, causing therebythe lever 19 toswing to the left and to start clock work 56. When the bolt 60 continuesits downward movement,

the pin 63 is pushed by the stop 1'! against the spring and is likewiseforced to the left. The. pin 63 actuates a flexible shaft I6 by means ofwhich the shutterof the object lens is released. At the same time, thecircuit 50 is closed through contacts 61 and 68, and the clock work 56begins to open, by means of toothed gear wheels 51, 58, 48, thecompletely closed diaphragm of the object lens 47 of the cell. The morethe diaphragm is opened the stronger will be the current which flowsthrough the circuit 50 of the photo-cell. When a predetermined strength"of current is reached, the armature 66 is attached by the magnet 55andthe bolt 60 is thereby released. The latter, by means of the spring6| is forced back into its dotted line position; At the same time, thepin 63 is forced back to the right by spring80 whereby the shutter ofthe camera is closed. And also the pin 63 is forced back to the right bythe spring 18, whereby the clockwork is stopped and the diaphragm of theobject lens 41 of the cell is completely closed. The resistance 54serves to regulate the circuit 50.

In case of exposures in which the object to be photographed showsconsiderable differences in brightness the photo cell should be adjustedonly to the dark portions of the picture. The pair of tubes 84, shouldtherefore be adjusted by means of the driver 14, 15 to reduce the angleof the picture until only the dark portions remain visible in the searchlens 13. In this way the exposing time is lengthened. Lens light willget into the cell, and the current in the circuit 50 will increaseslower in intensity. 1

While for convenience I have shown the invention as applied to a cameraof the box type, it will be understood that my invention may be employedin conjunction with other photo graphic apparatus where it is desired tocontrol a timing element in accordance with the intensity of a selectedbeam of.'light.-

I have chosen the particular embodiments described above as illustrativeof my invention, and it will be obvious that various other modificationsmay be made without departing from the spirit andscope of my'inven'tion,which modifications I intend to cover by the appended claims.

What l2 claim as new and desire to secure by Letters Patent of theUnited States, is:

l. The combination with a camera having a shutter and means operatingunder pressure to. 5 open the shutter and hold it in open position; of alatching mechanism for said shutter opening means and including a latchpin, an electromagnet associated with said latch pin to release thelatching means upon energization to a 10 predetermined extent, a sourceof current, a

light sensitive cell, conductive connections be- 2. The combination witha. camera having a 25' shutter and means operating under pressure toopen the shutter and hold it in open position; of

a latching mechanism for said shutter opening means and including alatch pin. an electromagnet associated with the said latch pin torelease 30 the latching means upon energization to a predeterminedextent, a source of current, a light sensitive cell, conductiveconnections between the electromagnet, source of current and cellconnecting them in series, a focusing lens for said 35 cell arranged toreceive light from the object to be photographed and focus it on thecell, and visually observable means for regulating the focusing of thelens on a definite part of such object.

3. .The combination with a camera having a 40 shutter biased to closedposition and means for opening-the shutter, means for holding theshutter in open position, a. light sensitive cell, a device responsiveto a predetermined output of the cell for releasing said shutter holdingmeans, 45 and means for uniformly varying the response of said cell.

4. The combination with a camera having a shutter biased to closedposition, means for opening the shutter and means for holding the shut-50 exposure, a light sensitive device responsive to 0 light of anintensity which bears a known ratio to the intensity of the exposinglight, means for uniformly increasing the intensity of the light fallingon said device, and means for actuating said exposure terminating meanswhen the re- 65 sponse of said device reaches a predetermined value.

ODON RISZDORFER.

